If you use exfoliating soaps, you might not know those little beads may be made of plastic -- or think about what happens to them when they go down the drain.

But it's on the minds of marine science researchers, as well as a major company.

Unilever, the company that makes Dove soaps, Vaseline, Pond's skin cream and other personal care products, announced recentlyit's phasing out the use of "plastic micro beads as a 'scrub' material" in its personal care products.

By 2015, the phase out should be complete, Unilever said. The company said the "the issue of plastics particles in the ocean is an important issue."

Research in microplastics suggests that very small particles, even tens of microns in diameter, can be retained in the tissues of marine invertebrates, Thompson said. A 2008 study from Thompson's group found that microplastic particles remained in mussels for 48 days.